1. Field of the Invention
The present invention relates generally to the field of heat dissipation devices known as heat sinks. More specifically the present invention relates to a heat sink including a chamber having a chamber first end wall and a chamber second end wall and a circumferential chamber side wall interconnecting the chamber first and second end walls, at least one of these walls being a heat transfer wall in thermal contact with a heat source, the chamber containing a heat transfer material and an impeller having radial blades for moving the material over the heat transfer wall and propelling the material to a heat exchange region thermally remote from the heat source for heat dissipation, the chamber being configured such that the impeller(s) gather and release liquid along liquid flow paths determined by the impeller rotation. In regions not swept by the impellers, high conductivity porous inserts can be included to ensure high heat transfer through the porous structure. The chamber of a first and second embodiments are closed and are differentiated by the heat transfer material. In the first embodiment, a liquid or similar flowable material is used, whereas in the second, a phase change heat transfer material is provided such that it melts with the heat received from the heat source, thereby becoming a flowable heat transfer material during operation. The chamber of a third embodiment has the general structure of the first and second embodiments except for the provision of a chamber entry port which gathers liquid from a location thermally remote from the heat source and external to the chamber and the chamber exit port delivers liquid to a heat exchange region external to the chamber.
2. Description of the Prior Art
A number of active and inactive heat transfer devices have been provided in the form of heat sinks and cold plates for transferring heat away from various electronic elements so that the temperatures of these devices remain within acceptable limits so that the devices operate at higher efficiency and require less shut down time for cooling. These have included simple heat sinks mounted on individual components to provide larger surface areas for enhanced dissipation of heat to the surrounding atmosphere either by natural or forced convection. For high power systems, entire boards have been mounted on liquid-cooled heat exchangers such as cold plates which transfer the waste heat to the atmosphere via a liquid-air radiator. The entire flow loops usually include pumps, valves, drive motors, or other components as required for specific applications.
Batchelder, U.S. Pat. No. 6,019,165, issued on Feb. 1, 2000 for a heat exchange apparatus teaches a chamber. However, in the embodiments of Batchelder, shown in Batchelder FIGS. 2 and 3, the impeller drives the heat transfer fluid radially outward from the center of the impeller through a network of heat exchange narrow passageways. Batchelder does not teach an open and unobstructed chamber interior for free and low resistance heat transfer flow. Batchelder does not teach the simple active heat sink configuration having an impeller with a path of impeller rotation and gathering heat and releasing transfer liquid along liquid flow paths determined by the impeller rotation.
Paterson, U.S. Pat. No. 5,390,077, issued on Feb. 14, 1995, discloses an integrated circuit cooling device having an internal baffle. Paterson includes a cooling fluid chamber which rests on top of a heat source and contains cooling fluid in both liquid and gaseous phases. The cooling fluid evaporates within the chamber, rises between two upwardly tapering barrier structures to emerge from the middle of these structures and make contact with cooler upper and side chamber walls having heat fins, where it condenses and falls back around the outer periphery of the barrier structures into the liquid phase pool of cooling fluid.
Remsburg, U.S. Pat. No. 5,864,466, issued on Jan. 26, 1999 teaches a thermosyphon-powered jet-impingement cooling device similar in general design to Paterson, except that the condensed cooling fluid returns to the pool of liquid fluid at the center of the barrier structure and causes a boundary layer minimizing jet action against the heat source abutting wall of the chamber.
Other liquid and gaseous fluid flow cooling devices found in the search are Schneider, et al., U.S. Pat. No. 5,950,714, issued on Sep. 14, 1999 for a tubular cooling apparatus for an electronic component, the tube containing a venturi member; Messina, U.S. Pat. No. 5,309,319, issued on May 3, 1994 for an integral cooling system for electric components; Mansingh, U.S. Pat. No. 5,020,586, issued on Jun. 4, 1991 for an air-cooled heat exchanger for electronic circuit modules; and Reichard, U.S. Pat. No. 5,316,077, issued on May 31, 1994 for a heat sink for electrical circuit components.
It is thus an object of the present invention to provide a heat sink apparatus having a simple and reliable construction including a chamber containing a heat transfer material in liquid or solid phase and an impeller having a path of impeller rotation and gathering heat and releasing liquid phase transfer material along liquid flow paths determined by the impeller rotation to a heat exchange region thermally remote from the heat source for heat dissipation.
It is another object of the present invention to provide such a heat sink apparatus which transfers heat away from a heat source with greater efficiency than existing cold plates by distributing liquid phase heat transfer material uniformly over the heat transfer wall adjacent to or adjoining the heat source so that there are no dead spaces in this region and mechanically forcing liquid phase heat transfer material flow within the thermal boundary layer of the liquid.
It is yet another object of this invention to provide such a heat sink apparatus which will have a thin plate like configuration that can be directly attached to a circuit board type device. In this case, heat from a localized heat source is gathered by the fluid driven by an adjacent impeller and transferred via the liquid flow to a heat exchange region thermally remote from the heat source for heat dissipation.
It is still another object of the present invention to provide such a heat sink apparatus in which very high heat transfer rates are possible over localized surface areas using independently controlled impellers, such that overall power requirement and system pressures are relatively low, both modular and integrated designs are feasible.
Another goal of this invention is to provide such a heat sink in which special liquid or solid phase heat transfer materials can be used in modules, and in which design is scalable.
Another object of this invention is to ease the manufacture and assembly of the heat sink. This is accomplished by using a phase change heat transfer material that is in its solid phase under normal ambient conditions, thereby eliminating problems associated with flowable (i.e. liquid) heat transfer materials. During operation, the phase change material absorbs heat from the heat source, melts, and the liquid phase is then used to transfer heat in an active mode.
It is yet another object of the present invention to provide a heat sink in which heat can be efficiently transferred through regions not swept by an impeller by conduction through porous inserts.
It is yet another object of the present invention to provide such a heat sink apparatus which provides an internal pumping effect so that the external pump may be omitted in many cases.
It is finally an object of the present invention to provide such a heat sink apparatus which is economical to manufacture and reliable.